Sulfuric acid olefin absorption



Patented Oct. 7, 1947 SULFURIC ACID OLEFIN ABSORPTION Henry J. Hibshman, Plainfield, and Insley P.

Jones, Basking Ridge, N. J., assgnors to Standard Oil Development Company, a corporation of Delaware Application September 15, 1943, Serial No. 502,442

4 Claims.

This invention relates to improvements in the absorption of olens and relates particularly to the absorption with sulfuric acid of olens that tend to polymerize and react with other olens in the presence of the said acid.

It is known that olens may be dissolved from a hydrocarbon mixture by contacting with sulfuric acid solutions and that these olens may be recovered by diluting and heating the acid solution. In the processing of a C4 cut, it is established practice to remove the isobutene first by contacting the hydrocarbon mixture with a sulfurie acid solution of approximately 65% concentration at a temperature of approximately 65 F. The residual hydrocarbons remaining consisting of butane, isobutane and normal butenes are then contacted With sulfuric acid of higher concentration at higher temperatures to remove the normal butenes present. Both of these acid extracts are diluted and heated With steam to recover overhead a gaseous mixture of butenes, polymer, alcohol, ether and water. This vapor .mixture is fractionated for the recovery of butenes. When sulfuric acid of 65% concentration is used at the temperature of 65 F., a substantial residue of the isobutene remains in solution in the hydrocarbon mixture unless prolonged periods of time of contact are used, with the result that a substantial quantity of the isobutenes is polymerized.

The object of this invention is to provide a method in which an isobutylene of 100% purity can be recovered.

Another object of the invention is to provide a method in which the corrosion resulting from the use of sulfuric acid of about 65% concentration is avoided.

These and other objects of the invention will be understood upon reading the following description with reference to the accompanying drawing.

Referring to the drawing in Figure 1, numeral I designates a preheater in which the heating fluid is introduced through inlet 2 and withdrawn through outlet 3. Invthepreheater is set a spray equipment which consists of pipe ll through which sulfuric acid is passed into a constricted orifice and pipe 5 through which a hydrocarbon gas containing the olefin is introduced. The preheated hydrocarbon gas and sulfuric acid are then forced through orifice 6, the hydrocarbon gas being in the vapor phase as it passes through orifice t is mixed with the sulfuric acid and the sulfuric acid is atomized. An atomized mixture of hydrocarbon gas and sulfuric acid gas is passed into reactor l Which is provided at its lower part with a separator 8 from which the hydrocarbon gas is Withdrawn through pipe 9 and the sulfuric acid extract through pipe I0 provided with valve Il,

A series of runs were made at atmospheric pressure with sulfuric acid of 'T0-98% concentration at E30-200 F. and 0.02 to 14 seconds contact time. Isobutylene removal up to 55% With 100% purity was effected, as illustrated by the following table:

3 Sec. Contact Time 5 Lbs/sq.

Operating Conditions Using 90% H2S04 with a 5 Lbs/sg. in. Orifice Pressure Drop Contact Time. scc 1 2 4 Per Cent of Isobutylcne Removed 50 68 8 5 Purity of Isobutylene Recovered 100 65 50 When the temperature of thefeed gas and acid was varied from to 200 F., no consistent changes in purity or recovery could be detected. These temperatures, however, refer to the preheater section vonly and do not necessarily apply to the reaction zone. The actual contact temperatures, therefore, calculated from known heats of absorption are probably more nearly in the range of 30G-400 F.

Most of the runs were made at a feed isobutylene/HzSOli mol ratio of 1, although the effect of this variable does not appear too critical over the range of 0.5 to 3 studied. The pressure drop across the orifice is important as indicated by the following data obtained with I-IzSOil at F.

Orice Pressure Drop, Lbs. per sq. in 0. 5 l 5 Per Cent of Isobutylene Removed 19 47 65 Purity of Isobutylene Recovered 100 100 99 I 3 tion 70% boils below 390 indicating it to be principally diand tri-isobutylene.

The drawing Figure 2 illustrates the relation between isobutylene removal by means of sulfuric acid and the contact time. That is, sulfurie acids of 80-98% concentration at relatively short periods of Contact time may be used vto .re-

move substantiallly the 'major fraction of iso'butyl-V ene in a mixture of hydrocarbons containing the said isobutylene. Furthermore, the isobutylene may be removed in step operations vas illustrated A by the following example: y Example A C4 cut containing 19.4% isobutylen'e, 35.1% n-butylenes and 45.5% saturated hydrocarbons was contacted in the vapor Vphase with .85% HzSOi (0.8 mole isobutylene/mol HzSOi) by spraying into areactor (2.2 sec. contact time at 150 F.). 50% of the isobutylene Was removed of 100% purity leaving a Ig-as containing .10.4% isobutylene, 50.5% n-'butylene fand-@925% saturated hydrocarbons. When this gas was contacted with Ymore"85% H2504, 65% ol fthe remaining isobutylene was removed of 73% puri-ty, leaving :a gas containing only 2.6% isobutylene and 47.3% n- -butylene The -n-bu'tylenes may be removed in a third step Vwhere the 4'contact time is increased to 5 to 2,0 seconds'and at least "501% of the n-butyl- -enes are removed in fthis 'third step. `The percent Vremoval of n-butylenes 'may be materially increased by increasing the contact time and/or the concentration of the acid as there is no great tendency of polymer formation.

We claim:

1. In the sulfuric acid absorption -of isobutylene, the improvement which 'comprises heating an isobuty-lene-containing hydrocarbon gas to a temperature ranging from 80-200 F., heating a sulfuric acid of 85-98% `concentration to a temperature ranging from 80-'200 F., commingling the hydrocarbon gas and the sulfuric acid in Aan atomized state for a period of time running from 0.02 to about 3 seconds, immediately separating unreacted vhydrocarbon gas from the sulfuric acid Aand recovering 'the isobutylene `from said acid.

2. inthe sulfuric acid absorption of isobutyleneythe improvement which comprisesheating 'one mol of isobutylene contained in a `mixture Aof Vsaturated `and unsaturated hydrocarbons and one 'molof sulfuric 4acid of 8598 l'concentration to a temperature ranging `from V8D-J200 Jand contacting the hydrocarbon in the vapor state and the sulfuric acid in an atcmized state 'for a period 'of time ranging from 0.2 to 3 seconds, immediately 'separating the unreactedhydrocarbons 4 from the sulfuric acid, diluting the sulfuric acid with water and heating to recover isobutylene.

3. In the sulfuric acid absorption of isobutylene, the improvement which comprisesheating one mol of isobutylene contained in a mixture of saturated and unsaturated hydrocarbons and one .mol of lsulfuric acid of `85-98"% concentration to a temperature ranging from 810-200V0 F. and contacting the hydrocarbon in the vapor Vstate and Y lthe sulfuric acid in an atomized state for a period Y of timeranging from 0.2 to 3 seconds, immediately separating the unreacted hydrocarbons from the'su'lfuric ac'id, diluting the sulfuric acid with water, heating to recover isobutylene, treating the lseparated hydrocarbons'with sulfuric acid of 85-"98% concentration, separating the unre Y .acted hydrocarbons V,from the sulfuric acid, diluting the sulfuric acid extract with Water and separating normal butylene. Y Y

- 4. In the sulfuric acid absorption of isobutyl-V ene, 4the improvement which comprises heating an lisobutylene-con'ta'ining hydrocarbon V-ga's fat. a temperature ranging `from F-200 F.,heating 'sulfuric acid of 85-'98% concentration to a temperature of 80-200" F., contacting the 'hydrocarlbon gas withvthe :sulfuric `acidV in an `-atomized V lstate 'fora 'period .of time ranging yfrom 0.2 to 3 seconds, immediately ksepara-ting the unreacted hydrocarbons from thesulfuric acid, treating the unreacted hydrocarbon fga's with another volume,

of sulfuric acid of 'B5-98% 'concentration for a :period of time'ranging from 0.2 tolseconds separating the unreacted hydrocarbons -'from the sulvfuri'c acid, diluting the :sulfuric aci-d extract with `water and heating to recover lisobutylene.

HENRY J. Iv-IfIBSl-IMAN. .INSLEY P. '-JONES.

Y REFERENCES CITED v rPhe following references are 'of 'record in the Ale of this patent:

.UNITED STATES PATENTS 

